A variety of additives are taught by the art as useful in controlling the gelation and/or cure of unsaturated resins, especially of unsaturated polyester resins. Great Britain 1,226,688 teaches low temperature cures using a combination of a metal accelerator, a polyamine and a peroxide or perester catalyst. Vanadium compounds in various combinations with peroxide and hydroperoxide catalysts and other accelerators are taught in U.S. Pat. Nos. 3,333,011 and 3,639,504. Other patents disclosing various cure/accelerator compositions include U.S. Pat. Nos. 2,822,344; 3,003,991; 3,079,363; 3,318,974; 3,238,274; 3,652,718; 3,239,581 and 3,737,480. Control of gelation with a peroxide catalyst by 2,4-pentanedione is disclosed in U.S. Pat. No. 3,653,954.
In general, resin systems which are accelerated (promoted) by the addition of metal compounds and the like are designed to cure more rapidly. However, the resin also gels more rapidly which makes it difficult to apply the resin because of the short working time. The problem is compounded when it is desired to formulate a resin which will cure at room temperature and is particularly complicated when cure at temperatures below 0.degree. C is required. For such curing conditions the amounts of catalyst and/or accelerator are increased which decrease the working time. Consequently, to avoid this pot life problem, mechanical means of application must be used which attempt to rapidly mix the components just prior to application. Such methods are difficult to control and in addition are more expensive.